Current gene therapy vectors employ animal viruses or condensed DNA/protein complexes to deliver DNA. The use of animal viruses has been limited because of tropism for normal cells, associated toxicity the cost of large-scale production, and the difficulty of genetically altering a complicated virus. Nonverbal systems offer an alternative but are difficult to produce with the same homogeneity of a virus. We aim to improve current gene therapy methods by developing an alternative gene delivery vehicle, the bacteriophage that is simple and economical to produce and lacks native tropism for mammalian cells. Having demonstrated that genetically targeted phage can transduce mammalian cells we propose here to add improved cell trafficking and other accessory peptides and DNA elements involved in trafficking, phage replication and integration to the phage vector with the goal of enhancing the transduction efficiency such that the targeted phage will be useful for gene therapy. We will then test the improved phage for delivery of a therapeutic gene in vivo using several tumor models. The long-term goal of this proposal is, therefore, to develop a safe, economical, and effective alternative to existing gene therapy vectors for therapeutic gene delivery to treat cancer and other diseases. PROPOSED COMMERCIAL APPLICATIONS: We propose to develop bacteriophage as an improved alternative to existing gene delivery methods. The commercial applications include reduced production costs and improved gene therapy of cancer and gene replacement therapy. Our strategy will be to genetically incorporate peptide and DNA elements that confer efficient mammalian cell tropism on a bacteriophage vector. The vector will be targeted to specific receptor bearing cells using a ligand that is displayed on the tip of the phage particle as a genetic fusion to a phage coat protein. We will test the improved vector in an in-vivo disease model to demonstrate the use of phage as a safe and effective alternative vehicle for therapeutic gene delivery.